Electrical apparatus



' G. CAMILLI ELECTRICAL APPARATUS 2 Sheets-Sheet 1 Filed July 28, 1944 T10 Cami! Ii,

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rfiventorfi Guglie by W Hi5 Attorne June 18, 1946.

ELECTRICAL APPARATUS Filed July 28, 1944 2 Sheets-Sheet 2 Inventor'- Guglielmo Carnil Ii,

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torney.

Patented June 18, 1946 ELECTRICAL APPARATUS Guglielmo Camilli, Pittsfield, Mass, assignor to General Electric Company, a corporation of New York Application July 28, 1944, Serial No. 547,044

11 Claims. 1

My invention relates to electrical apparatus such as transformers, and although not limited thereto it has application to high voltage potential transformers.

Electrical induction apparatus such as transformers and reactors have been formed by providing a winding of a plurality of turns of a conductor, the winding being insulated with insulation of the solid porous type such as crepe paper. The winding is then placed along with a suitable core member into a casing which is filled with an insulating dielectric such as oil. When impregnating the solid porous insulation which surrounds the winding with the oil it is necessary so as to obtain the highest electrical characteristics of the composite insulation to remove all impurities such as moisture, air, etc. When employing a very compact winding structure which includes a plurality of concentric layers of conductor, each layer formed by a plurality of turns considerable difiiculty was encountered in removing gaseous impurities from the Winding when a layer of insulation relatively closely surrounds and encloses the winding turn. Thus as described and claimed in my Patent 2,297,606, issued September 29, 1942, and assigned to the same assignee as this present invention, the removal of the gaseous impurities is facilitated by providing a fluid passage which communicates outside the insulating covering and also connects inside the insulating layer, particularly near the top, Any tube arrangement can be provided and a convenient way is to provide a hollow electrical connection between the winding and the terminal through which the gases may be withdrawn.

As a winding such as the type described in my above-mentioned patent is designed for higher and higher voltage more layers of compact insulation are provided around the concentric conductor layers and an improved arrangement for providing such layer insulation is described in my patent application Serial No. 467,225, filed November 28, 1942, and assigned to the same assignee as this present invention (now Patent No. 2,359,544, dated October 3, 1944). Such a high voltage coil, as is described and claimed in my cop'ending application, includes interlayer insulation between the concentric conductor layers which are sufficiently long so as to be folded around the outside conductor layer which is usually connected during operation to the highest potential.

Thus I have found it desirable to provide additional arrangements for removing gaseous impurities in the vicinity of the winding turns parti-cularly when a relatively thick insulating layer is provided around the winding turns such as of the type described in my above-mentioned copending application which includes a plurality of folded layers, and it is therefore an object of my invention to provide an improved arrangement for removing any gaseous impurities before and during impregnation of the insulated winding with the insulating fluid, such as oil.

A further object of my invention is to provide an improved electrical apparatus which is simpie to manufacture and efficient in operation and which is particularly simple for high voltages.

Further objects and advantages of my invention will become apparent from the following description referring to the accompanying drawings, and the features of novelty which characterize my invention will be pointed out with particularity in the claims annexed to and forming a part of this specification.

In the drawings Fig. 1 is a side view in partial section illustrating a transformer which is provided with an embodiment of my invention; Fig. 2 is a sectional end elevation of one of the high voltage windings employed in the construction of Fig. 1, and Fig. 3 is a sectional side elevation of one of the insulated high voltage windings of the type illustrated in Fig. 2.

Referring more particularly to Fig. 1 of the drawings I have illustrated an electrical apparatus which has particular application as a transformer, such as a high voltage potential transformer, but it will be understood that my invention has application to any other suitable type of electrical apparatus. The construction includes a high voltage winding indicated generally by the numeral Ill which will be described in further detail below. Concentric with the high voltage winding Hi there is provided a low voltage winding l which in turn surrounds a winding leg 12 of a core construction, the yoke portion of the core construction being shown as 13. Surrounding the core and coil construction I provide a casing M which, it will be seen, is relatively small and follows the contour of the winding so as to minimize the volumetric capacity of the casing, Extending through the casing is an insulated terminal construction 15 which connects with the high voltage winding H! which will be described below. Surrounding the insulated terminal construction Hi there is provided a bushing it which is in turn supported on a collar [1 of a tubular member 18 which extends from the closing casing M. A terminal I9 is provided which is electrically connected to the end of the insulated lead construction I5. In the construction there is also provided a bushing 2%] similar to the bushing l6 which encloses a similarsecond terminal construction which is connected with the high voltage end of a high voltage winding which is similar and concentric to Winding IS, a portion of which is shown by the numeral 2| in Fig. 3. However, since both of the winding structures l and 2| are similar only one will be described,

As will be seen more clearly in Figs, 2 and 3 the high voltage winding includes a plurality of concentric conductor layers 25. Any suitable number of these layers may be provided depending upon the voltage on which the transformer is designed to operate. In order suitably to insulate the concentric layers it will be noted that between some of the layers is provided insulation 26 which is sufiiciently long so as to be folded around the outermost conductor layer 21 as is indicated at 28. Such a construction provides an eflicient insulated concentric layer wound transformer which has a very high creepage strength and which construction is described and claimed in my above-mentioned copending application. Further insulation 30 is provided around the various layers of insulation which. may be provided in the manner also described in the above-mentioned application by peripherally winding a sheet of insulation such as paper around the high voltage winding and bending the edges over as is illustrated at 3|. Any suitable additional amount of insulation may be wound around the high voltage windings I0 and 2| by providing insulation 32 by winding the insulation through and around the doughnut shaped coil.

In order to provide an arrangement for removing gaseous impurities from inside the insulation,

the insulation layers which it will be seen closely surround and enclose the winding and thereby restrict the passages through which gaseous impurities may be removed, I provide a chamber 35 which is outside the conductor layer 21 such as substantially surrounding it. This chamber may be provided in any suitable manner such as by providing spaced walls 36 and 31 which are perforated as is indicated b the numeral 38. Although these walls may be formed of any suitable material, since such a high voltage transformer is usually provided with an electrostatic shield, I provide the walls 36 and 31 of a suitable conducting material such as a metallic screen which thereby serves the dual purpose of pro viding an electrostatic shield as well as forming a chamber. Thus gases which are to be removed from around the winding turns and inside the tightly enclosing insulation may be collected in the hollow chamber 35. A conductor layer 39 may be provided around the coil to act as a ground shield.

In order to remove such gaseous impurities from the chamber of the electrostatic shield during treating of the transformer I provide any suitable type of passage means such as the one disclosed and claimed in my above-mentioned patent. Thus as will be seen, particularly in Fig. 2, I provide a tubular member 40 which communicates inside the chamber 35 an which also connects with a second tube 4|. This second tube as will be seen in Fig. 1 passes through the bushing l6 into the vicinity of the terminal l9. Electrical connection between the terminal cap and the winding may be made in an suitable manner and in the construction as illustrated in Figs.

l and 2 I provide a conductor 43 which has one end 44 connected to the terminal cap l9 and a second end 45 connected to the tube 40. The tube 40 is made of conducting material and connects with the outer end of the adjacent conductor layer 21 as shown by the connector 46 in Fig. 3. Suitable connection may also be made with the connector 46 and the high voltage shield arrangement 36 and 31 as it is conventional to connect the high voltage electrostatic shield to the adjacent high voltage winding.

It will therefore be seen that even though a relatively large thickness of tightly compacted layers of insulating material are provided around the high voltage winding that a convenient arrangement is provided which includes a circumferentially extending chamber into which gaseous impurities may be collected before they are withdrawn through the tubes 40 and 4|. A convenient way of removing gaseous impurities is to place the core and coil construction within the casing l4, insert the bushings and make electrical connection between the terminal cap and the conductor 43. Such a casing and bushing may then be hermetically sealed or provide a relatively tightly enclosed casing therefor. Since the terminal 9 is hollow by having a passage 50 extending therethrough which is enclosed by a cap 5|. by removing the cap 5| and drawing a vacuum through the hollow terminal gases and impurities may be withdrawn from the space outside the insulation and inside the casing as well as inside the insulation. Since the top of the tube 4| does not extend to the top of the bushing it will be seen that drawing a vacuum through the passageway 50 will accomplish th withdrawal of the impurities from both inside the insulating layer and outside the layer and between the insulating layer and the surrounding casing I4. When substantially all gaseous impurities have been removed a suitable dielectric fluid such as oil may then be introduced into the casing from the bottom such as through the hole 52 after removing the plug 53. This oil may then be introduced very slowly so that it will permeate through the layers of insulation around the winding. It will further be seen that any gaseous impurities such as air or moisture which might remain in the insulation layers or between the conductor layers will be drawn into the chamber with the perforated electrostatic shield since a vacuum may be maintained through the hollow terminal while the liquid is being introduced. Furthermore, the slowly rising liquid will displace the impurities which will naturally tend to collect in the chamber 35 which impurities may be removed. After a suitable amount of oil has been placed in the structure such as up to the level 56. the plug 53 may be inserted in the hole 52 and cap 5| placed in the hole in the end of the terminal. This construction is then suitably impregnated with substantially all impurities removed.

It may also be desirable when a relatively large amount of insulation is placed around the coils to provide additional passageways through which the impurities may be withdrawn from the relatively large thickness of insulation and in the construction illustrated in the drawings it will be noted that the insulation 32 is provided with a plurality of ducts 6|]. These ducts may be provided in any suitable manner such as by winding on a suitable amount of insulation and then providing spacers not shown and then Winding on a second layer of insulation and continuing this by interdispersing ducts throughout the insulation 32. A duct BI is also provided in the insulation 30 lead I5 and tube 4| which insulation is provided,

with ducts 63 which communicate with the ducts 60 and BI. It will be understood that the insulation 62 may be provided at the same time the insulation 32 is placed on the winding by wrapping a plurality of layers of suitable insulating,

material through and around the coil and also around the terminal lead l5.

It will therefore be seen that when such an insulated winding is put in the casing l4 and a" vacuum is drawn through the passageway 50 in the terminal that gas and any moisture or impurities will be withdrawn from the ducts 60 and SI. Furthermore, when the transformer is impregnated with the dielectric fluid such as oil, such fluid will fill the ducts 6!] and BI and provide the dielectric strength within the ducts. It will also be seen that there will be a certain amount of movement of fluid in the ducts 60 and GI thus contributing to cooling the winding I0.

Although I have shown and described particular embodiments of my invention, I do not desire to be limited to the particular embodiments described, and I intend in the appended claims to cover all modifications which do not depart from the spirit and scope of my invention.

What I claim as new and desire to secure by Letters Patent of the United States is:

1. An electrical apparatus including a winding having a plurality of turns, a layer of insulation relatively closely surrounding and substantially enclosing said Winding and thereby restricting passages through which gaseous impurities may be removed, an electrostatic shield surrounding said Winding inside said insulation, said shield having spaced walls providing a chamber with said winding wholly outside said chamber,

and means providing a passage having an opening in said shield chamber and communicating outside said layer of insulation, said shield means being perforated so that gaseous impurities may be withdrawn through said shield and passage means.

2. An electrical apparatus including a winding having a plurality .of turns, a layer of insulation relatively closely surrounding and substantially enclosing said winding turns, a perforated electrostatic shield substantially surrounding said turns inside said layer of insulation, said shield having spaced Walls providing a chamber with said winding wholly outside said chamber, and a tube communicating with said perforated shield and outside said layer of insulation.

3. An electrical apparatus including a winding having a plurality of turns, a layer of insulation relatively closely surrounding and substantially enclosing said winding turns, a perforated electrostatic shield providing a chamber substan tially surrounding said turns inside said layer of insulation, said Winding being wholly outside said chamber, a terminal for said winding, a connectionbetween said terminal and said winding, said connection being hollow and adapted to communicate outside said insulating layer and communicating with said shield chamber so that gas may be withdrawn.

4. An electrical apparatus including a winding having a plurality of turns, insulation relatively closely surrounding and substantially enclosing said winding turns and thereby restricting passages through which gaseous impurities may be removed, perforated mean providing a chamber extending substantially around said winding turns inside said insulation, said winding being wholly outside said chamber, and passage means communicating with said chamber and outside said insulation so that gaseous impurities may be withdrawn.

5. An electrical apparatus including a winding having a plurality of concentric conductor layers, said conductor layers being connected in series so that the outer layer is adapted to have the highest voltage during operation, layer insulation between conductor layers and extending along the edges of said layers and around the outer conductor layer so as to provide a relatively compact insulated high voltage winding, said insulation also restricting passages through which gaseous impurities may be withdrawn from between conductor layers inside said compact insulation, means providing a chamber adjacent the surface of the outer of said concentric conductor layers, said winding being wholly outside said chamber, and passage means communicating with said chamber and outside said compact insulation so that gaseous impurities may be Withdrawn.

6. An electrical apparatus includin a winding having a plurality of turns, a layer of insulation relatively closely surrounding and substantially enclosing said winding turns, perforated means inside said insulation providing a chamber substantially surrounding said winding turns, said winding being wholly outside said chamber, and passage means communicating with said chamber and outside said insulation so that gas may be withdrawn from said winding through said perforated means to said chamber and out said passage means.

7. An electrical apparatus including a winding having a plurality of turns, insulation around said winding turns, conducting means having spaced walls providing a chamber surrounding the outer surface of said turns and inside said insulation, said turn being wholly outside said chamber, said means having perforations, and passage means connecting with said chamber and outside said insulation so that gas may be withdrawn from inside said insulation through said perforated means and out said passage.

8. An electrical apparatus including a winding having a plurality of turns, insulation around said winding turns, conducting means having spaced walls providing a chamber outside said turns and inside said insulation, said turns being Wholly outside said chamber, said means having perforations, and passage means connecting with said chamber and outside said insulation so that gas may be Withdrawn from inside said insulation through said perforated means and out said passage, said conducting means being connected to said winding so as to act as an electrostatic shield for said apparatus.

9. An electrical apparatus including a plurality of winding turns, insulation around said winding turns, means providing a chamber outside said turns and inside said insulation, said turns being Wholly outside said chamber, tube means communicating outside said insulation, a second conducting tube communicating with said tube means, a terminal for said winding, means electrically connecting said second tube with said winding and said terminal to provide a lead, said '7 second tube communicating with said chamber so that gas may be withdrawn through said second and first tubes.

10. An electrical apparatus including a winding having a, plurality of turns, a layer of insulation relatively closely surrounding and substantially enclosing said winding turns, a perforated electrostatic shield substantially surrounding the outer surface of said turns inside said layer of insulation, said shield having spaced walls forming a chamber with said turns wholly outside said chamber, and a tube communicating with said perforated shield and outside said layer of insulation, means providing a duct within said layer of insulation, and means providing a passage communicating with said duct and outside said insulation so that gaseous impurities may be withdrawn through said shield and said duct.

11. In an electrical apparatus, a winding having a plurality of conductor layers, a. conductor lead connected to said winding, a layer of insulation relatively closely surrounding and substantially enclosing said winding and a portion of said lead and thereby restrictin passages through which gaseous impurities may be withdrawn from between said winding layers, means providing a duct within said layer of insulation surrounding said winding, said winding being wholly outside of said duct, a casing enclosing said insulated Winding, a bushing on said casing and surrounding said insulated conductor lead, said bushing having an opening through which gaseous impurities may be withdrawn from said insulated winding, and means providing a second duct within said lead insulation and communicating with said winding duct and said opening in said bushing for facilitating the removal of gaseous impurities from within said insulating covering.

GUGLIELMO CAMILLI. 

